This invention relates to improvement of surface combustion type burners with single-stage air supply thus entirely as primary air, equipped with metallic netting defining the combustion surface, particularly to such burners suited for high combustion load.
As conventional burners of the surface combustion type there are various different ones as to the way how to provide the combustion surface, thus utilizing therefor a formed ceramic product, metallic netting and so forth, each of them having the respective advantages and disadvantages. It is apparent, however, that those utilizing the metallic netting are practically more favorable than those utilizing the formed ceramic product, in view of lower material cost and of better productivity owing to easy forming operation. As included in such conventional burners utilizing the metallic netting, there indeed are different structures as using the netting in a single layer and in two or more overlapping layers, but they have all been the burners for rather low combustion load. The reason for such restriction in using such type of burners is that the higher the combustion load the more eminent becomes the problems of the higher noxious exhaust NO.sub.x content and the higher tendency of causing backfire owing to excessive burner heating, while that the more excessively supplied the primary air in the intention of thereby solving such problems the higher becomes the tendency of causing lift of the flame to thus result in the higher noxious exhaust CO content. Consequently, it has conventionally been compelled to use such burners in low combustion load range with restricted supply of the air.